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1Laboratory of Metabolism, Division of Endocrinology, Diabetology, and Nutrition, Department of Internal Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland. 2Department of Pharmacology, German Institute of Human Nutrition Potsdam-Rehbrucke, Nuthetal, Germany. 3Department of Psychiatry, Obesity Research Center, University of Cincinnati, Cincinnati, Ohio, USA. 4Department of Cell Physiology and Metabolism, Faculty of Medicine, and 5Department of Rehabilitation and Geriatrics, University of Geneva School of Medicine, Geneva, Switzerland.
Abstract
Many homeostatic processes, including appetite and food intake, are controlled by neuroendocrine circuits involving the CNS. The CNS also directly regulates adipocyte metabolism, as we have shown here by examining central action of the orexigenic hormone ghrelin. Chronic central ghrelin infusion resulted in increases in the glucose utilization rate of white and brown adipose tissue without affecting skeletal muscle. In white adipocytes, mRNA expression of various fat storage–promoting enzymes such as lipoprotein lipase, acetyl-CoA carboxylase , fatty acid synthase, and stearoyl-CoA desaturase–1 was markedly increased, while that of the rate-limiting step in fat oxidation, carnitine palmitoyl transferase–1, was decreased. In brown adipocytes, central ghrelin infusion resulted in lowered expression of the thermogenesis-related mitochondrial uncoupling proteins 1 and 3. These ghrelin effects were dose dependent, occurred independently from ghrelin-induced hyperphagia, and seemed to be mediated by the sympathetic nervous system. Additionally, the expression of some fat storage enzymes was decreased in ghrelin-deficient mice, which led us to conclude that central ghrelin is of physiological relevance in the control of cell metabolism in adipose tissue. These results unravel the existence of what we believe to be a new CNS-based neuroendocrine circuit regulating metabolic homeostasis of adipose tissue.
Introduction
Neuroendocrine circuits within the CNS that are known to regulate appetite and food intake have also been shown to be involved in the control of peripheral metabolism and thermogenesis. A recent series of elegant studies demonstrates that some of the hypothalamic circuits regulating energy balance also specifically sense macronutrient availability (1–3), thereby triggering efferent signals that adjust peripheral homeostatic processes, such as glucose and lipid metabolism (4–6). The hypothalamic melanocortin system, including the neuropeptides agouti-related protein (AgRP) and -melanocyte–stimulating hormone, is one of the circuits involved in the CNS control of peripheral glucose homeostasis (7). Hypothalamic neuropeptide Y (NPY) also affects peripheral glucose and lipid metabolism (8, 9). Both the melanocortin system and NPY are known hypothalamic targets of the gastrointestinal hormone and putative neuropeptide ghrelin (10–18).
Apart from its role as a growth hormone secretagogue, exogenous ghrelin administration causes a positive energy balance and increases body weight when administered pharmacologically (10, 19, 20). A physiological role for endogenous ghrelin is suggested by the fact that genetic deletion of ghrelin or its only known receptor results in decreased susceptibility to high-fat diet–induced obesity (21, 22). This effect was observed despite the simultaneous deletion of the recently discovered ghrelin-associated satiety factor, obestatin (23), in these knockout mice. However, the phenotype of ghrelin gene–disrupted mice only becomes apparent upon chronic exposure to a high-fat diet, indicating a possibly impaired ability to store excess dietary fat in the absence of ghrelin action.
Ghrelin synthesis and secretion are regulated by the nutritional state (24–26). Thus food intake as well as the administration of glucose or other nutrients decreases circulating ghrelin levels, while caloric restriction or food deprivation increases these levels (19, 27, 28). The extent and functional relevance of brain-derived ghrelin still needs to be clarified (15–18, 29). However, the orexigenic and adipogenic effects of centrally administered ghrelin are potent and consistent (10, 19, 30).
In the present study we investigated whether central ghrelin influences peripheral metabolism and whether these effects are dependent on its orexigenic action. More specifically, the aims of our study were to determine the effects of central ghrelin administration on insulin sensitivity in peripheral tissues, lipid metabolism in white adipose tissue (WAT), and thermogenesis-related processes in brown adipose tissue (BAT). Other aims were to propose a possible mechanism for such central effects of ghrelin on peripheral cell metabolism and to determine the potential relevance of such effects for endogenous ghrelin.
We demonstrate here that central ghrelin increased food intake and independently regulated adipocyte metabolism. In white adipocytes it favored glucose and triglyceride (TG) uptake, increased lipogenesis, and inhibited lipid oxidation. In brown adipocytes icv ghrelin decreased the expression of uncoupling proteins (UCPs), which usually contribute to energy dissipation. These ghrelin effects were dose dependent and seemed to be mediated by the sympathetic nervous system. We additionally observed that the expression of some fat storage enzymes was decreased in ghrelin-deficient mice.
Results
Effects on energy balance. Chronic icv ghrelin infusion (2.5 nmol/d for 6 days) increased food intake in ad libitum–fed rats (ghrelin–ad lib) compared with icv saline–infused controls (Figure 1A). A second control group consisted of icv ghrelin–infused animals that were pair-fed to the food intake of the saline-infused controls (ghrelin-pf). Body weight gain of icv ghrelin–ad lib rats was significantly higher than that of both the control and the ghrelin-pf groups (Figure 1B). Ghrelin treatment increased food efficiency, calculated as the ratio of body weight gain to cumulative food intake measured, during the 6-day experimental period (Figure 1C). The increase in body weight in icv ghrelin–infused rats was related to a higher fat mass gain, as determined by NMR imaging (Figure 1D), without any change in lean body mass (data not shown). Indirect calorimetry was used to determine whether changes in energy expenditure also contribute to the ghrelin-induced weight gain. Chronic icv ghrelin treatment did not alter total energy expenditure or spontaneous physical activity, but resulted in a significant increase in the respiratory quotient (RQ), indicative of elevated fat deposition (Table 1).
10.1172/JCI25811DS1). In only one exception, red quadriceps, was glucose uptake higher in icv ghrelin-pf animals than in icv ghrelin–ad lib animals or controls (Supplemental Table 1). During the clamps, hepatic glucose production was comparably suppressed by hyperinsulinemia in all groups (data not shown).
Figure 2
Effect of a 6-day icv ghrelin infusion (2.5 nmol/day) on insulin-stimulated glucose utilization indices measured during euglycemic-hyperinsulinemic clamps in epididymal WAT (A ), inguinal WAT (B ), BAT (C ), and soleus muscle (D ). Values are mean ± SEM of 6–7 animals per group. *P < 0.05 versus control; #P < 0.05 versus ghrelin-pf.
Effects on white adipocyte metabolism. Chronic icv ghrelin infusion increased glucose uptake in both epididymal and inguinal WAT depots (Figure 2, A and B) compared with controls. Such central ghrelin-induced stimulation of insulin-dependent glucose uptake in adipose tissue was independent of hyperphagia, as it was also observed in icv ghrelin-pf animals. In a separate experiment, the impact of icv ghrelin on several key enzymes of adipocyte lipid metabolism was assessed. As depicted in Figures 3 and 4, icv ghrelin infusion markedly increased mRNA levels of the fat storage–promoting enzymes lipoprotein lipase (LPL), acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), and stearoyl-CoA desaturase–1 (SCD1) in ghrelin–ad lib and ghrelin-pf animals. In contrast, the fat oxidation–promoting enzyme carnitine palmitoyl transferase–1 (CPT-1) was decreased in icv ghrelin–ad lib rats (Figure 3C). Low-density RNA microarrays, another method to determine the mRNA expression of the same enzymes, produced remarkably similar results as those generated by real-time PCR, although the primers used were different in the two techniques (Supplemental Table 2). Finally, the relevance of the observed changes at the transcriptional level was also confirmed by Western blotting for FAS and SCD1 (Figure 4, C and D), showing increased protein levels under the influence of icv ghrelin.
Figure 3
Effect of a 6-day icv ghrelin infusion (2.5 nmol/d) on epididymal WAT mRNA expression of LPL (A ), ACC (B ), and CPT-1 (C ). Data are presented as values normalized to RPS29, which was used as a housekeeping gene. Values are mean ± SEM of 6–7 animals per group. *P < 0.05 versus control; #P < 0.05 versus ghrelin-pf.
Figure 4
Effect of a 6-day icv ghrelin infusion (2.5 nmol/d) on epididymal WAT mRNA expression of FAS (A ) and SCD1 (B ), as well as on epididymal WAT FAS (C ) and SCD1 (D ) protein expression, with 1 representative Western blot (of the 2 performed). Data in C and D are presented as values normalized to calreticulin, which was used as a housekeeping gene. Values are mean ± SEM of 6–7 animals per group. *P < 0.05 versus control; #P < 0.05 versus ghrelin-pf.
Hepatic mRNA expression of ACC, FAS, and CPT-1 was unaltered, indicating specificity of the observed effect for WAT (data not shown). However, SCD1 mRNA levels were more than doubled in the liver of both icv ghrelin–infused groups compared with controls.
Effects on brown adipocyte metabolism. As occurred in WAT, icv ghrelin infusion promoted an increase in insulin-stimulated glucose utilization in BAT independent of hyperphagia (Figure 2C). To test the hypothesis that central ghrelin administration influences energy metabolism in brown adipocytes, we determined the mRNA expression of UCP1 and UCP3 in BAT. Central ghrelin infusion markedly decreased the expression of UCP1 in both ghrelin-infused groups (Figure 5). Similar results were observed for UCP3, although the decrease in the icv ghrelin–ad lib group was at the limit to reach statistical significance.
Table 4
Effects of peripheral ghrelin infusion on mRNA expression of ACC, FAS, SCD1, LPL, and CPT-1 in epididymal WAT and UCP1 and UCP3 in BAT
Possible mediating mechanism and relevance for endogenous ghrelin function. As mentioned in the Introduction, NPY is the main target of ghrelin action within the hypothalamus. In the present experiment, icv ghrelin infusion (2.5 nmol/d for 6 days) resulted in increased hypothalamic NPY mRNA expression as expected, and this occurred even in the absence of hyperphagia (Figure 6). As central NPY is known to modulate the activity of the autonomic nervous system, specifically, to inhibit the activity of some sympathetic efferents (e.g., those innervating BAT; ref. 31), we examined central ghrelin action in the absence of sympathetic nervous system signaling. For this purpose, we treated WT and triple ?1-, ?2-, and ?3-adrenoceptor knockout (TKO) mice with icv ghrelin following the same protocol as that described above (2.5 nmol/d for 6 days). As expected, icv ghrelin administration increased body weight gain in WT animals, while identical icv ghrelin treatment in TKO animals had no effect on body weight gain (Figure 7, C and D). There was no ghrelin effect on cumulative food intake in WT or TKO mice, although there was a trend toward an increase in WT mice (Figure 7, A and B). Indicative of a possible dependence of icv ghrelin-induced regulation of adipocyte metabolism on the efferent sympathetic nervous system, ghrelin failed to change mRNA expression of FAS (87.4% ± 36.8% of control; values normalized by cyclophilin A, used as a reporter gene; P = NS) and UCP1 (117.2% ± 33.3% of control; values normalized by cyclophilin A, used as a reporter gene; P = NS) in adipose tissue of TKO mice.
Figure 6
Effect of a 6-day icv ghrelin infusion (2. 5 nmol/d) on hypothalamic NPY mRNA expression. alues are mean ± SEM of 6–7 animals per group. *P < 0.05 versus control.
Figure 7
Effect of a 6-day icv ghrelin infusion (2. 5 nmol/day) on cumulative food intake (A andB ) and body weight gain (C andD ) in WT and TKO mice. Values are mean ± SEM of 5–6 animals per group. *P < 0.05 versus control.
To further examine whether the above-described observations are indicative of an essential endogenous role for ghrelin in the regulation of WAT metabolism, we analyzed adipocyte metabolism of ghrelin-deficient mice. Interestingly, expression patterns opposite to those observed during icv ghrelin treatment were identified, reflecting a possible physiological role of ghrelin in the control of WAT metabolism. Specifically, we observed a decrease in LPL and SCD1 mRNA expression in ghrelin KO mice compared with WT controls (Figure 8), while food intake, body weight, and body fat did not differ between ghrelin-deficient mice and their WT littermates, which were all on a chow diet during the whole study.
3,000 dilution; Sigma-Aldrich) antibodies for 1 hour at room temperature. Immunoreactive bands were visualized by enhanced chemiluminescence reaction (for FAS and calreticulin antibodies, LiteAblot; Euroclone; for SCD1 antibody, Super Signal West Dura; Pierce Biotechnology; Fisher Scientific International Inc.). Bands were quantified by Quantity One System (Bio-Rad). FAS and SCD1 protein amount was expressed relative to calreticulin expression.
Levels of plasma metabolites and hormones. Plasma glucose was measured by the glucose oxidase method (glucose analyzer 2; Beckman Coulter). Plasma FFA concentrations were determined using a kit from Wako; TGs were determined using a kit from bioMérieux. Plasma insulin levels were measured by a previously described RIA (68). Plasma levels of other hormones were determined by commercial RIA kits from Linco for leptin and active ghrelin and from IDS for corticosterone. These measurements were performed on samples that were collected in fed animals around 5 hours following cessation of feeding.
Statistics. Results are given as mean ± SEM. Statistical analysis was performed using 1-way ANOVA followed by the post-hoc Tukey test. All calculations were performed using SigmaStat 3.0 (SPSS). A 2-tailed P value less than 0.05 was considered statistically significant.
Acknowledgments
This work was carried out thanks to grant no. 3100A0-105889 of the Swiss National Science Foundation. It was part of the Geneva Program for Metabolic Disorders. It was also supported by the European Community (EC) FP6 funding (contract no. LSHM-CT-2003-503041) for F. Rohner-Jeanrenaud and M.H. Tsch?p. It should be mentioned that the publication reflects the authors’ views and not necessarily those of the EC. The information in this document is provided as is and no guarantee or warranty is given that the information is fit for any particular purpose. The user thereof uses the information at its sole risk and liability. We wish to thank Marcella Klein, Sarah Mouche, Traci Kruthaupt, and Sabine Strassburg for excellent technical and scientific assistance. We wish to thank the Genomics Platform of the National Centre of Competence in Research Frontiers in Genetics program for the invaluable help in performing the low-density array experiments. Finally, we are indebted to Steve Woods, Tim Bartness, Craig Hammond, Silvana Obici, and Randy Seeley for very insightful discussions and editing of our manuscript.
References
Akabayashi A., Koenig J.I., Watanabe Y., Alexander J.T., Leibowitz S.F. 1994. Galanin-containing neurons in the paraventricular nucleus: a neurochemical marker for fat ingestion and body weight gain. Proc. Natl. Acad. Sci. U. S. A. 91:10375–10379.
Wortley K.E., Chang G.Q., Davydova Z., Leibowitz S.F. 2003. Peptides that regulate food intake: orexin gene expression is increased during states of hypertriglyceridemia. Am. J. Physiol. Regul. Integr. Comp. Physiol. 284:R1454–R1465.
Lam T.K., et al. 2005. Hypothalamic sensing of circulating fatty acids is required for glucose homeostasis. Nat. Med. 11:320–327.
Obici S. and Rossetti L. 2003. Minireview: nutrient sensing and the regulation of insulin action and energy balance. Endocrinology. 144:5172–5178.
Wortley K.E., Chang G.Q., Davydova Z., Fried S.K., Leibowitz S.F. 2004. Cocaine- and amphetamine-regulated transcript in the arcuate nucleus stimulates lipid metabolism to control body fat accrual on a high-fat diet. Regul. Pept. 117:89–99.
Yun R., et al. 2005. PVN galanin increases fat storage and promotes obesity by causing muscle to utilize carbohydrate more than fat. Peptides. 26:2265–2273.
Obici S., et al. 2001. Central melanocortin receptors regulate insulin action. J. Clin. Invest. 108:1079–1085 doi: 10.1172/JCI200112954.
Zarjevski N., Cusin I., Vettor R., Rohner-Jeanrenaud F., Jeanrenaud B. 1993. Chronic intracerebroventricular neuropeptide-Y administration to normal rats mimics hormonal and metabolic changes of obesity. Endocrinology. 133:1753–1758.
Zarjevski N., Cusin I., Vettor R., Rohner-Jeanrenaud F., Jeanrenaud B. 1994. Intracerebroventricular administration of neuropeptide Y to normal rats has divergent effects on glucose utilization by adipose tissue and skeletal muscle. Diabetes. 43:764–769.
Nakazato M., et al. 2001. A role for ghrelin in the central regulation of feeding. Nature. 409:194–198.
Tschop M., Statnick M.A., Suter T.M., Heiman M.L. 2002. GH-releasing peptide-2 increases fat mass in mice lacking NPY: indication for a crucial mediating role of hypothalamic agouti-related protein. Endocrinology. 143:558–568.
Chen H.Y., et al. 2004. Orexigenic action of peripheral ghrelin is mediated by neuropeptide Y and agouti-related protein. Endocrinology. 145:2607–2612.
Kojima M., et al. 1999. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 402:656–660.
Kojima M. and Kangawa K. 2005. Ghrelin: structure and function. Physiol. Rev. 85:495–522.
Turek F.W., et al. 2005. Obesity and metabolic syndrome in circadian Clock mutant mice. Science. 308:1043–1045.
Cowley M.A., et al. 2003. The distribution and mechanism of action of ghrelin in the CNS demonstrates a novel hypothalamic circuit regulating energy homeostasis. Neuron. 37:649–661.
Hu Z., Cha S.H., van Haasteren G., Wang J., Lane M.D. 2005. Effect of centrally administered C75, a fatty acid synthase inhibitor, on ghrelin secretion and its downstream effects. Proc. Natl. Acad. Sci. U. S. A. 102:3972–3977.
Mozid A.M., et al. 2003. Ghrelin is released from rat hypothalamic explants and stimulates corticotrophin-releasing hormone and arginine-vasopressin. Horm. Metab. Res. 35:455–459.
Tschop M., Smiley D.L., Heiman M.L. 2000. Ghrelin induces adiposity in rodents. Nature. 407:908–913.
Dornonville de la Cour C., et al. 2005. Ghrelin treatment reverses the reduction in weight gain and body fat in gastrectomised mice. Gut. 54:907–913.
Wortley K.E., et al. 2005. Absence of ghrelin protects against early-onset obesity. J. Clin. Invest. 115:3573–3578 doi: 10.1172/JCI26003.
Zigman J.M., et al. 2005. Mice lacking ghrelin receptors resist the development of diet-induced obesity. J. Clin. Invest. 115:3564–3572 doi: 10.1172/JCI26002.
Zhang J.V., et al. 2005. Obestatin, a peptide encoded by the ghrelin gene, opposes ghrelin’s effects on food intake. Science. 310:996–999.
Tschop M., et al. 2001. Circulating ghrelin levels are decreased in human obesity. Diabetes. 50:707–709.
Otto B., et al. 2001. Weight gain decreases elevated plasma ghrelin concentrations of patients with anorexia nervosa. Eur. J. Endocrinol. 145:669–673.
Williams D.L. and Cummings D.E. 2005. Regulation of ghrelin in physiologic and pathophysiologic States. J. Nutr. 135:1320–1325.
Tschop M., et al. 2001. Post-prandial decrease of circulating human ghrelin levels. J. Endocrinol. Invest. 24:RC19–RC21.
Cummings D.E., et al. 2001. A preprandial rise in plasma ghrelin levels suggests a role in meal initiation in humans. Diabetes. 50:1714–1719.
Wortley K.E., et al. 2004. Genetic deletion of ghrelin does not decrease food intake but influences metabolic fuel preference. Proc. Natl. Acad. Sci. U. S. A. 101:8227–8232.
Kim M.S., et al. 2004. Chronic central administration of ghrelin reverses the effects of leptin. Int. J. Obes. Relat. Metab. Disord. 28:1264–1271.
Egawa M., Yoshimatsu H., Bray G.A. 1991. Neuropeptide Y suppresses sympathetic activity to interscapular brown adipose tissue in rats. Am. J. Physiol. 260:R328–R334.
Niswender K.D., Baskin D.G., Schwartz M.W. 2004. Insulin and its evolving partnership with leptin in the hypothalamic control of energy homeostasis. Trends Endocrinol. Metab. 15:362–369.
Dhillo W.S. and Bloom S.R. 2004. Gastrointestinal hormones and regulation of food intake. Horm. Metab. Res. 36:846–851.
Lutz T.A. 2005. Pancreatic amylin as a centrally acting satiating hormone. Curr. Drug Targets. 6:181–189.
King P.J. 2005. The hypothalamus and obesity. Curr. Drug Targets. 6:225–240.
Benoit S.C., Clegg D.J., Seeley R.J., Woods S.C. 2004. Insulin and leptin as adiposity signals. Recent Prog. Horm. Res. 59:267–285.
Gottero C., et al. 2004. Ghrelin: a link between eating disorders, obesity and reproduction. Nutr. Neurosci. 7:255–270.
Ueno H., Yamaguchi H., Kangawa K., Nakazato M. 2005. Ghrelin: a gastric peptide that regulates food intake and energy homeostasis. Regul. Pept. 126:11–19.
Tannenbaum G.S., Lapointe M., Beaudet A., Howard A.D. 1998. Expression of growth hormone secretagogue-receptors by growth hormone-releasing hormone neurons in the mediobasal hypothalamus. Endocrinology. 139:4420–4423.
Cowley M.A. and Grove K.L. 2004. Ghrelin--satisfying a hunger for the mechanism. Endocrinology. 145:2604–2606.
Yasuda T., Masaki T., Kakuma T., Yoshimatsu H. 2003. Centrally administered ghrelin suppresses sympathetic nerve activity in brown adipose tissue of rats. Neurosci. Lett. 349:75–78.
Lawrence C.B., Snape A.C., Baudoin F.M., Luckman S.M. 2002. Acute central ghrelin and GH secretagogues induce feeding and activate brain appetite centers. Endocrinology. 143:155–162.
Tang-Christensen M., et al. 2004. Central administration of ghrelin and agouti-related protein (83-132) increases food intake and decreases spontaneous locomotor activity in rats. Endocrinology. 145:4645–4652.
Barazzoni R., et al. 2005. Ghrelin regulates mitochondrial-lipid metabolism gene expression and tissue fat distribution in liver and skeletal muscle. Am. J. Physiol. Endocrinol. Metab. 288:E228–E235.
McGregor I.S., Menendez J.A., Atrens D.M. 1990. Metabolic effects of neuropeptide Y injected into the sulcal prefrontal cortex. Brain Res. Bull. 24:363–367.
Billington C.J., Briggs J.E., Grace M., Levine A.S. 1991. Effects of intracerebroventricular injection of neuropeptide Y on energy metabolism. Am. J. Physiol. 260:R321–R327.
Billington C.J., Briggs J.E., Harker S., Grace M., Levine A.S. 1994. Neuropeptide Y in hypothalamic paraventricular nucleus: a center coordinating energy metabolism. Am. J. Physiol. 266:R1765–R1770.
Levine A.S., Jewett D.C., Cleary J.P., Kotz C.M., Billington C.J. 2004. Our journey with neuropeptide Y: effects on ingestive behaviors and energy expenditure. Peptides. 25:505–510.
Sainsbury A., et al. 1997. Chronic central neuropeptide Y infusion in normal rats: status of the hypothalamo-pituitary-adrenal axis, and vagal mediation of hyperinsulinaemia. Diabetologia. 40:1269–1277.
Le Marchand Y., Freychet P., Jeanrenaud B. 1978. Longitudinal study on the establishment of insulin resistance in hypothalamic obese mice. Endocrinology. 102:74–85.
Cusin I., et al. 1990. Hyperinsulinemia increases the amount of GLUT4 mRNA in white adipose tissue and decreases that of muscles: a clue for increased fat depot and insulin resistance. Endocrinology. 127:3246–3248.
Guillaume-Gentil C., Assimacopoulos-Jeannet F., Jeanrenaud B. 1993. Involvement of non-esterified fatty acid oxidation in glucocorticoid-induced peripheral insulin resistance in vivo in rats. Diabetologia. 36:899–906.
Cusin I., Rouru J., Rohner-Jeanrenaud F. 2001. Intracerebroventricular glucocorticoid infusion in normal rats: induction of parasympathetic-mediated obesity and insulin resistance. Obes. Res. 9:401–406.
Colombo M., Gregersen S., Xiao J., Hermansen K. 2003. Effects of ghrelin and other neuropeptides (CART, MCH, orexin A and B, and GLP-1) on the release of insulin from isolated rat islets. Pancreas. 27:161–166.
Broglio F., et al. 2003. Effects of ghrelin on the insulin and glycemic responses to glucose, arginine, or free fatty acids load in humans. J. Clin. Endocrinol. Metab. 88:4268–4272.
Date Y., et al. 2001. Ghrelin acts in the central nervous system to stimulate gastric acid secretion. Biochem. Biophys. Res. Commun. 280:904–907.
Matsuda M., Aono M., Moriga M., Okuma M. 1991. Centrally administered NPY stimulated gastric acid and pepsin secretion by a vagally mediated mechanism. Regul. Pept. 35:31–41.
Geoghegan J.G., et al. 1993. Intracerebroventricular neuropeptide Y increases gastric and pancreatic secretion in the dog. Gastroenterology. 105:1069–1077.
Bamshad M., Aoki V.T., Adkison M.G., Warren W.S., Bartness T.J. 1998. Central nervous system origins of the sympathetic nervous system outflow to white adipose tissue. Am. J. Physiol. 275:R291–R299.
Penicaud L., Cousin B., Leloup C., Lorsignol A., Casteilla L. 2000. The autonomic nervous system, adipose tissue plasticity, and energy balance. Nutrition. 16:903–908.
Bartness T.J., Kay Song C., Shi H., Bowers R.R., Foster M.T. 2005. Brain-adipose tissue cross talk. Proc. Nutr. Soc. 64:53–64.
Bachman E.S., et al. 2002. betaAR signaling required for diet-induced thermogenesis and obesity resistance. Science. 297:843–845.
Jimenez M., et al. 2002. Beta(1)/beta(2)/beta(3)-adrenoceptor knockout mice are obese and cold-sensitive but have normal lipolytic responses to fasting. FEBS Lett. 530:37–40.
Rohner-Jeanrenaud F., Walker C.D., Greco-Perotto R., Jeanrenaud B. 1989. Central corticotropin-releasing factor administration prevents the excessive body weight gain of genetically obese (fa/fa) rats. Endocrinology. 124:733–739.
Terrettaz J., Assimacopoulos-Jeannet F., Jeanrenaud B. 1986. Severe hepatic and peripheral insulin resistance as evidenced by euglycemic clamps in genetically obese fa/fa rats. Endocrinology. 118:674–678.
Cusin I., Terrettaz J., Rohner-Jeanrenaud F., Jeanrenaud B. 1990. Metabolic consequences of hyperinsulinaemia imposed on normal rats on glucose handling by white adipose tissue, muscles and liver. Biochem. J. 267:99–103.
Vettor R., Zarjevski N., Cusin I., Rohner-Jeanrenaud F., Jeanrenaud B. 1994. Induction and reversibility of an obesity syndrome by intracerebroventricular neuropeptide Y administration to normal rats. Diabetologia. 37:1202–1208.
Herbert V., Lau K.S., Gottlieb C.W., Bleicher S.J. 1965. Coated charcoal immunoassay of insulin. J. Clin. Endocrinol. Metab. 25:1375–1384.